The Impact Of Energetic Tropical Cyclones (Typhoons) On The Modern Sediment Magnetism Along The South China Coast

Tropical cyclones (TCs) often affect the surface sediments of coastal areas, and impact the sediment imprint. Although the sediment magnetism is sensitive to coastal changes, the understanding of the coastal magnetic minerals' redistribution affected by TCs is far from adequate. Here, the magnetic and grain-size records from the seafloor sediments along the Leizhou Peninsula coast in South China before and after two violent TCs (Mangkhut and Barijat) occurred in September 2018 are present. The magnetic minerals mainly consist of magnetite, hematite, and goethite. For most sites, the content of hematite increased compared to magnetite and the magnetic minerals became coarser after the TCs subsided, while the amount of fine clay (<2 mu m) decreased and the amount of coarse sand (500-2000 mu m) increased. This is due to the preferential deposition of the lamellae hematite from the soils and the enhanced hydrodynamic transportation of suspended sediments. The mangrove forest resists the change to a certain degree, especially in the Leizhou Bay. The magnetic and grain-size properties are sensitive to the TC-induced deposits, and provide convincing tools to aid in detecting the paleo-TC activity in tropical coastal regions.